Apparatus for production of casting moulds

ABSTRACT

Apparatus for making inner and outer casting mould parts of settable mould material and shaped for forming elongated castings having substantially congruent transverse cross-sections along their lengths comprises a stationary outer shell that serves as a form for the outer wall of the outer mould part and has a length exceeding the length of the casting. An annular pattern shaped in cross-section to conform to the cross-sectional shape of the casting and an inner shell that serves as a form for the inner wall of the inner mould part, both of which are of a length substantially less than the length of the casting, are mounted for movement axially of the outer shell such that the pattern and inner shell can be positioned successively at different positions along the length of the outer shell to enable the mould parts to be made in a series of sequential stages section by section.

United States Patent Ordqvst 1 Oct. 10, 1972 [54] APPARATUS FOR PRODUCTION OF 1,431,524 10/ 1922 l-lillman et al. ..425/63 CASTING MOULDS Primary Examiner-J. Spencer Overholser [72] Inventor. glgdcfibert Ordqvst, Karlstad, Assistant E .ner Dewalden w. Jones Attomey-Brumbaugh, Graves, Donohue & Raymond [73] Assignee: Aktieboleget Karlstatk Melutniska Werkstad, Karlstad, Sweden [57] ABSTRACT [22] Filed: Feb. 18, 1971 Apparatus for making inner and outer casting mould [211 p. No "6559 parts of settable mould material and shaped for form- [30] Foreign Application Priority Date March 31, 1970 Sweden ..4420/70 [52] US. Cl ..425/63, 249/20 [51] int. Cl. ..B28b l/14 [58] Field of Search ..425/63, 214, 64; 249/17, 18, 249/33, 34, 160,188, 189, 20, 22

[56] References Cited UNITED STATES PATENTS 1,062,040 5/1913 Sellman ..42S/63 947,160 1/1910 Newerf ..425/63 825,183 7/1906 Bovee ..249/20 ing elongated castings having substantially congruent transverse cross-sections along their lengths comprises a stationary outer shell that serves as a form for the outer wall of the outer mould part and has a length exceeding the length of the casting. An annular pattern shaped in cross-section to conform to the cross-sectional shape of the casting and an inner shell that serves as a form for the inner wall of the inner mould part, both of which are of a length substantially less than the length of the casting, are mounted for movement axially of the outer shell such that the pattern and inner shell can be positioned successively at different positions along the length of the outer shell to enable the mould parts to be made in a series of sequential stages section by section.

5 Claims, 1 Drawing Figure If F APPARATUS FOR PRODUCTION OF CASTING MOULDS BACKGROUND OF THE INVENTION This invention relates to apparatus for making casting moulds and, in particular, for forming elongated inner and outer casting mould parts that are used to make elongated hollow castings having substantially congruent transverse cross-sections along their lengths.

The building of moulds for making large size elongated castings, such as so-called Yankee dryer cylinders used in certain types of paper-making machines, has always been a laborious and time consuming operation. A common method of producing casting moulds of this type involves constructing the mould parts separately by hand from firebrick and then coating the firebrick with a layer of clay mortar. The firebrick structure of the outer mould part is usually constructed within a cylindrical metal shell, which provides the strength required in the casting operation, and the inner surface of the firebrick is coated with clay mortar to a thickness of about 20 or 30 millimeters, the mortar layer being shaped, sized and smoothed using a scraping and smoothing blade which is rotated on an axis coaxial with the cylindrical inner surface. The surface of the mortar layer is then dressed with a moulddressing material. The inner part of the mould is also built up of firebricks by hand, the outer surface then being coated with a clay mortar layer, smoothed and dressed in much the same way as the outer mould part. One of the mould parts is then lifted up above the top of the other part and lowered into position to provide the annular space that forms the mould cavity into which the molten iron is poured in the casting operation.

Another known mould-building procedure involves the use of blocks or sections made of a suitable settable mould material. Although the use of relatively large blocks or sections for the mould parts permits some time saving in constructing the mould by eliminating some of the handwork and finishing required in making firebrick moulds, this mould-building technique requires manufacturing blocks with radii and thicknesses appropriate for the various diameters of the Yankee dryer cylinders to be produced. A significant part of the saving in actual fabrication of the final mould is offset by the operations involved in making the blocks or sections.

Among the disadvantages of previously known methods for producing large-size casting moulds, such as those used in the manufacture of Yankee dryer cylinders, are, first, the costly and time-consuming work involved. Constructing a large casting mould and allowing it to dry and set ordinarily takes about 8 to 10 weeks. Secondly, the clay mortar layer that provides the mould surface is not sufficiently rigid to eliminate a substantial amount of swelling that occurs when the molten iron is in the process of solidifying, particularly in the phase when graphite is precipitated. Consequently, the final cast cylinder requires considerable machining, and the manufacture of the mould must take into account an additional tolerance for machining allowance. This, in turn, increases the time and cost of machining the casting.

SUMMARY OF THE INVENTION There is provided, in accordance with the invention, apparatus for producing large casting moulds for Yankee dryer cylinders and for other large-size castings having transverse cross-sections that are congruent along the length of the casting. The apparatus comprises a stationary outer shell that serves as a form for the outer surface of the outer mould part and as a structural part of the outer mould part. The shell is of a length somewhat greater than that of the final casting to be made. An annular pattern shaped and dimensioned in cross-section substantially to conform to the cross-sectional shape and dimensions of the casting and an inner shell having an outer surface defining a form for the inner wall of the inner mould part are mounted within the outer shell in appropriately spaced relation to define the inner and outer surfaces of the outer and inner mould parts, respectively. The pattern and the inner shell are both of a length substantially less than the length of the casting, and are mounted for movement axially of the outer shell such that they can be positioned successively at different positions along the length of the outer shell to enable the mould parts to be progressively cast in sections.

Preferably, the outer shell, pattern, and inner shell are mounted with their axes oriented vertically, and the mould parts are made in sections beginning at the bottom. After a given section of the inner and outer mould parts is formed, the pattern and inner shell are raised vertically to another position, another section of both the inner and outer mould parts is formed, and the procedure is repeated until the entire length of the mould parts is completed. The pattern and the inner shell can also be moved continuously and gradually upward as the parts are progressively formed.

The apparatus, according to the invention, offers a number of advantages. For one thing, it reduces the time required for manufacturing the casting moulds to approximately half of the time that is required following conventional, previously known methods. Moreover, the moulds can be manufactured with greater accuracy and from materials more resistant to the expansion of the iron that occurs when graphite precipitation takes place as the molten iron solidifies and cools. The greater accuracy to which the casting can be formed enables tolerances to be reduced, thus saving material and reducing the time required for machining. The mould produced using the apparatus of the invention is substantially stronger than a mould built up from firebricks or separately cast sections, since it is essentially monolithic and free of the joints that tend to weaken multiple-piece moulds. The greater strength enables the moulds to resist hydraulic pressure generated by the molten iron during casting. lnasmuch as the mould parts resist swelling of the iron and endure relatively higher hydraulic pressures, the pressure developed in the iron as it is solidifying and cooling tends to force iron into voids that tend to be generated in connection with formation of dendrite. Thus, the tendency for voids to be left as a result of dendrite formation, a problem which has presented some difficulty since it cannot be compensated for by using risers because of the relatively large distances and consequent pressure loses involved in large castings, is substantially eliminated.

DESCRlPTlON OF THE DRAWING For a better understanding of the invention, reference may be made to the accompanying drawing, which is a cross-sectional side view taken generally along a plane through the axis of the apparatus, the view being generally schematic and showing the apparatus in a configuration it occupies during an intermediate stage in the sequence of making the complete mould parts.

DESCRIPTION OF AN EXEMPLARY EMBODlMENT The apparatus comprises a cylindrical outer shell 1 that is of a length somewhat greater than the length of the casting moulds to be produced. For purposes of description, the embodiment of the apparatus will be considered as being employed to manufacture inner and outer casting mould parts used to cast Yankee dryer cylinders used in certain types of paper-making machines. These cylinders are generally to feet in diameter and up to about 20 feet in length. Preferably, the shell 1 is manufactured from steel and is, of course, of a diameter somewhat greater than the diameter of the dryer cylinder to be manufactured, inasmuch as its inner surface serves as a form for the outer wall of the outer mould part. The shell is supported in a vertical position on an annular base plate 3, which in turn is supported on blocks 5.

A centrally located supporting column 7 is positioned coaxially with the outer shell 1 with its lower end supported on a centering and positioning pin 9 and its upper end aligned and held in position by several radially extending cables 11, each of which is preferably provided with a turnbuckle, that are secured to the upper end of the shell 1 at circumferentially spacedapart locations. It is preferable also to provide locating and supporting cables (not shown) extending radially and downwardly from points at the upper perimeter of the shell down to connectors on the floor of the foundry.

The column 7 receives an annular, one-way sliding and mounting device 13 that in turn supports a spider 15, the device 13 and spider 15 constituting a mounting structure for supporting and rigidly positioning a pattern 17. The pattern is an annular shell dimensioned and shaped to provide a mould cavity 39 that matches the cross-sectional shapes and dimensions of the dryer cylinder to be cast in the mould. The structure also carries a secondary pattern part 19 located inside and at the top of the main pattern 17 and appropriately shaped and dimensioned to form a mould cavity portion for producing an inwardly extending flange at the upper end of the Yankee dryer cylinder. The structure of the spider 15 is such that it is provided with spacedapart supporting points along the column to ensure that it does not tip or otherwise become misaligned with the axis of the column 7.

The device 13 may be of any of a number of suitable types of devices that enable the spider to be moved upwardly only and to be supported against downward movement, once having been moved into a given position from a position lower down on the column. Such types of devices permit the equipment to be used in self-supporting configuration, rather than requiring the spider and patterns to be held vertically in position by auxiliary lifting and holding equipment. An expandable, toothed conical wedge or a ratchet-type mechanism is appropriate for the device 13, and the details of such devices need not be described here, since they are per se well-known to those skilled in the an.

The pattern 17 is mounted in depending relation on the peripheral portion of the spider 15 and is of a length substantially less than the length of the mould parts to be produced. Also mounted in depending relation from the spider 15 is an inner shell 21 that serves as a form for the inner surface of the inner mould part. The shell 21 is also of a length substantially less than the length of the cylinder and preferably is of a length equal to the pattern 17. The space 31 between the outer shell 1 and the pattern 17 and the space 35 between the pattern and the inner shell 21 define cavities for moulding the mould parts.

The manufacture of the mould parts with the apparatus illustrated in the drawing is commenced by first constructing on the base plate 3 an annular bottom closure or ring 25, which may be made of concrete as a structural base and covered with firebricks. An annular mould insert 27 of generally L-shape in cross-section is then positioned on top of the base 25, the insert 27 serving as a form for creating a space at the lower end of the mould structure for the formation of an inwardly extending, annular flange at one end of the dryer cylinder. Next, the outer shell 1 is positioned on the base plate, and the column 7 and structure lowered into position using the lifting eyes 23in the structure 15 and the foundry overhead crane, for example. The column is adjusted and fixed in the proper coaxial relation to the shell 1. The structure 15 is then moved into its lowermost position on the column 7 so that the lower ends of the pattern 17 and inner shell 21 engage the base 25 of the mould, such lowermost position being illustrated by dashed lines in the drawing.

The outer mould part 33 and inner mould part 37 are formed in stages, each stage involving depositing a settable mold material in the space 31 between the outer sleeve 1 and the pattern 17 and the space 35 between the pattern 17 and the inner sleeve 21 to a level (e.g., the level designated in the drawing by the reference numeral 29) just below the lower edge of the secondary pattern part 19. The mould material is either rodded or vibrated to ensure that it fully fills the spaces and is then permitted to set. The apparatus may be employed to make moulds of any of a number of known materials, such as those based on silica or olivine sands and binders such as bentonite, and other clays, hydrocarbon binders, resinous binders (e.g., furan) or water glass.

The structure 15 is then moved upwardly in small steps using hydraulic jacks or any other suitable lifting equipment. Once the structure 15 has been moved to a given vertical position, the device 13 permits it to be self'supporting on the column 7, and the lifting equipment need not remain in place. The foregoing procedure of sequentially positioning the pattern 17 and the shell 21 at succeeding vertical locations one above the other and forming at each location an additional section of each of the mould parts is repeated until the mould parts reach their required vertical dimension. Preferably, the structure 15 is moved in very small steps (not the entire length of the pattern) or continuously; otherwise the pattern may fasten as the mould material is setting.

As part of the final filling of the mould parts for the uppennost sectionythe entire vertical spaces defined between the shell 1, the pattern 17, and the inner shell 21 are filled, including the relatively narrow space radially inwardly of the secondary pattern part 19. The additional part 19 provides a mould cavity portion for forming an inwardly extending flange at the upper end of the dryer cylinder and a portion of a riser of appropriate dimensions and form. This completes the forming of the inner and outer mould parts and the structure and the column 7 can be removed, thus leaving the mould parts in place.

The final finishing of the mould parts is accomplished by lifting up the outer shell 1 and the outer mould part 33 together until they clear the upper end of the inner mould part 37 and then transferring them to another location so that the inner wall of the outer mould part can be dressed. This leaves the outer wall of the inner mould part 37 exposed for dressing also. The mould parts are then reassembled by lifting the outer part 33 back into place and positioning and fixing the mould parts in proper relation to each other. If the mould parts have not fully hardened when they are put together they are allowed to set up completely before casting the cylinder.

The above described embodiment of the invention is intended to be exemplary, and those skilled in the art will be able to make numerous variations and modifications without departing from the spirit and scope of the invention. For example, the apparatus according to the invention may be employed for making moulds to produce various large castings of any shape based on a straight axis and substantially congruent transverse cross-section. All such variations and modifications are intended to be included within the scope of the invention, as defined in the appended claims.

I claim:

1. Apparatus for making inner and outer casting mould parts of a settable mould material and shaped for forming elongated hollow castings having substantially congruent transverse cross-sections along their lengths comprising a stationary outer shell having an inner surface defining a form for the outer wall of the outer mould part and having a length exceeding the length of the casting, an annular pattern shaped and dimensioned in transverse cross-section substantially to conform to the cross-sectional shape and dimensions of the casting and having a length substantially less than the length of the casting; an inner shell having an outer surface defining a form for the inner wall of the inner mould part and having a length substantially less than the length of the casting, and means mounting the pattern and the inner shell within the outer shell in spaced relation for movement axially of the outer shell, whereby the pattern and inner shell are adapted to be positioned successively at different positions to enable the mould parts to be made in sections of lengths substantially less than the total lengths thereof.

2. Apparatus according to claim 1 wherein the outer shell, pattern and inner shell are mounted with their A par tii a diding to claim 2 wherein the mounting means includes a vertical supporting column having a length greater than the length of the casting and mounted within the outer shell, and a structure supported by the column for vertical movement thereon and carrying the pattern and the inner shell in depending relation.

4. Apparatus according to claim 3 wherein the mounting means further includes means connected to the outer shell and to the column for positioning the column relative to the shell.

5. Apparatus according to claim 3 wherein the structure is mounted on the column for upward movement only, the mounting means including means for supporting the structure on the column against downward movement, whereby the structure is supported on the column at a position once it has been moved up from another position below such position. 

1. Apparatus for making inner and outer casting mould parts of a settable mould material and shaped for forming elongated hollow castings having substantially congruent transverse cross-sections along their lengths comprising a stationary outer shell having an inner surface defining a form for the outer wall of the outer mould part and having a length exceeding the length of the casting, an annular pattern shaped and dimensioned in transverse cross-section substantially to conform to the cross-sectional shape and dimensions of the casting and having a length substantially less than the length of the casting; an inner shell having an outer surface defining a form for the inner wall of the inner mould part and having a length substantially less than the length of the casting, and means mounting the pattern and the inner shell within the outer shell in spaced relation for movement axially of the outer shell, whereby the pattern and inner shell are adapted to be positioned successively at different positions to enable the mould parts to be made in sections of lengths substantially less than the total lengths thereof.
 2. Apparatus according to claim 1 wherein the outer shell, pattern and inner shell are mounted with their axes disposed vertically.
 3. Apparatus according to claim 2 wherein the mounting means includes a vertical supporting column having a length greater than the length of the casting and mounted within the outer shell, and a structure supported by the column for vertical movement thereon and carrying the pattern and the inner shell in depending relation.
 4. Apparatus according to claim 3 wherein the mounting means further includes means connected to the outer shell and to the column for positioning the column relative to the shell.
 5. Apparatus according to claim 3 wherein the structure is mounted on the column for upward movement only, the mounting means including means for supporting the structure on the column against downward movement, whereby the structure is supported on the column at a position once it has been moved up from another position below such position. 